Update s3transfer to 0.2.0

This PR updates [s3transfer](https://pypi.org/project/s3transfer) from **0.1.13** to **0.2.0**.



<details>
  <summary>Changelog</summary>
  
  
   ### 0.2.0
   ```
   =====

* feature:``ProcessPoolDownloader``: Add ``ProcessPoolDownloader`` class to speed up download throughput by using processes instead of threads.
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/s3transfer
  - Changelog: https://pyup.io/changelogs/s3transfer/
  - Repo: https://github.com/boto/s3transfer
</details>

Author: pyup-bot

requirements.txt

@@ -57,9 +57,9 @@ boto3==1.9.89 \
 botocore==1.12.86 \
     --hash=sha256:5b01a16f02c3da55068b3aacfa1c37dd8e17141551e1702424b38dd21fa1c792 \
     --hash=sha256:24444e7580f0114c3e9fff5d2032c6f0cfbf88691b1be3ba27c6922507a902ec
-s3transfer==0.1.13 \
-    --hash=sha256:c7a9ec356982d5e9ab2d4b46391a7d6a950e2b04c472419f5fdec70cc0ada72f \
-    --hash=sha256:90dc18e028989c609146e241ea153250be451e05ecc0c2832565231dacdf59c1
+s3transfer==0.2.0 \
+    --hash=sha256:7b9ad3213bff7d357f888e0fab5101b56fa1a0548ee77d121c3a3dbfbef4cb2e \
+    --hash=sha256:f23d5cb7d862b104401d9021fc82e5fa0e0cf57b7660a1331425aab0c691d021
 python-dateutil==2.8.0 \
     --hash=sha256:7e6584c74aeed623791615e26efd690f29817a27c73085b78e4bad02493df2fb \
     --hash=sha256:c89805f6f4d64db21ed966fda138f8a5ed7a4fdbc1a8ee329ce1b74e3c74da9e